You are out the door cruising around the neighborhood. Nothing can stop you--except maybe that dead feeling in your legs. And that empty feeling in your stomach.

What you eat--or don't eat--for breakfast can make or break your running.

The alarm sounds, and you roll out of bed and into your running shoes. Within minutes, you are out the door cruising around the neighborhood. Nothing can stop you--except maybe that dead feeling in your legs. And that empty feeling in your stomach. And the fact that no matter how hard you push, your normal nine-minute pace quickly stalls into a laborious 10-minute-plus shuffle.

Often times it's a mystery why a good run goes bad. But any nutritionist can tell you in just two words what's going on in a dead-leg morning slog: no breakfast. "Running in the morning without eating something is like driving a car on fumes," says Jenna Bell-Wilson, R.D., a nutrition and exercise instructor at the University of New Mexico in Albuquerque. According to Bell-Wilson, when you run in the a.m. without eating breakfast, your pace will feel harder than it is, you won't be able to reach higher intensities, and you'll burn fewer calories as your body goes into conservation mode from the lack of fuel in your system.

This all happens because, unless you're a midnight snacker, you've been fasting for nine to 12 hours between dinner and sunup. During this time, your muscle and liver glycogen and blood-glucose levels drop--all crucial energy sources that fuel your running. By eating shortly after you awake, you break the fast and begin to top off your energy stores. With a full tank, your body is then primed for exercise.

Reams of research have confirmed that breakfast eaters, whether they run or not, are healthier and trimmer than people who blow off breakfast. Studies show that morning eaters are better able to manage their weight, mostly because they're less likely to become ravenous, and therefore overeat later in the day.

Breakfast also helps control blood-sugar levels, which increases your mental acuity and improves mood. And researchers are studying how certain foods eaten at breakfast may affect our hormones and ultimately help prevent chronic diseases.

Some fast runners even attribute their breakthrough performances to their a.m. meal. Marathoner Dan Browne, who'll be representing the United States at the Olympics this summer, fuels up on breakfast before every big event. "I ran my fastest marathon after eating store-bought rice pudding and coffee," says Browne. "I'll be looking for rice pudding in Athens this summer. Normally though, I have coffee, a banana, and a Clif Bar."

Breakfast foods that work for one runner--rice pudding, say--may not sit well with another. Most runners need to experiment to find out which foods work best for them. "My favorite breakfast is black tea with milk and sugar, and a plain bagel, half with cream cheese and half with peanut butter and jelly," says middle-distance runner and two-time Olympian Amy Rudolph.

The American College of Sports Medicine and the American Dietetic Association recommend eating a high-carbohydrate, 400- to 500-calorie meal two or three hours before exercise. Jennifer Toomey, Olympic hopeful and U.S. record holder in the 1000 meters, cooks herself a hearty breakfast every morning. "Pretty much every day, I'll have two fried eggs, two slices of whole-wheat toast, OJ, and coffee," she says. That's fine if you have the time before you run, but it's not practical for early morning runners. If that's you, tailor your breakfast to your workout. A mini meal or snack of 100 to 300 calories is plenty for runs of up to an hour at a moderate pace. Just 16 ounces of sports drink, one energy gel, or eight ounces of your favorite juice will do the trick.

Whatever calorie count you're aiming for, the best breakfast foods are rich in complex and simple carbohydrates and high-quality protein, with smaller amounts of healthy fats. This combination of nutrients will set you up for better running no matter what time of day you head out.

What's For Breakfast

Here are five quick mini-breakfasts, ranging from about 200 to 400 calories, that deliver plenty of carbohydrates, plus protein and good fats to keep your energy levels higher, longer.

Stone-Wheat Crackers with Nut Butter--Spread a thin layer of almond, cashew, or good ol' peanut butter on four whole-wheat crackers.

A Meal Replacement Beverage--If you're not interested in solid food in the morning, grab a meal in a bottle, such as those by Snapple or Slim-Fast.

Oatmeal á la Rice Cooker--Rice cookers make great old-fashioned oatmeal and will cook on a timer so that it can wake you up when it's finished cooking. For added protein, top it off with a dollop of yogurt or peanut butter.

Two Handfuls of Trail Mix--Choose one that contains nuts, fruit, and some cereal or pretzels. This amount packs more than 250 calories, but offers a good combination of fat, protein,and carbohydrates.

Sports Bar--Most energy bars make a decent breakfast. Look for one with at least 200 calories and 6 grams of protein. Most PowerBars, Cliff Bars, or Balance Bars will fit the bill.